Pitot-static tube



Aug- 26, 1941- w. A. RElclzHEl. 2,254,155

PITOT-STATIC TUBE Filed- Dec. 13, 1958 INVENTOR.

ATI'ORN EY.

Patented Aug. 26, 1941 PITOT- STATIC TUBE Wladimir A. Reichel, Bellerose, N. Y., assignor to Bendix Aviation Corporation,

South Bend, Ind.,

a, corporation of Delaware Application December 13,1938, serial No. 245,501

(Cl. 'Z3-212) 2 Claims.

The present invention relates to Pitot-static tubes and more particularly to Pitot-static tubes for use on aircraft in` conjunction with indicating or control devices. n

The invention embodies a novel combination of a Pitot-static tube and means for maintaining said tube free of sleet, snow, ice or other impedimenta. n

More specically the means embodying the invention are provided for the purpose of heating a Pitot-static tube ina novel manner whereby high heating emciency is produced and the Pitotstatic tube is maintained in perfect operating.

condition under all climatic conditions.

Similar devices of the prior art havebeen.

utilized but they have had a low heating eiciency,

failing, therefore, to produce a proper operating Vstatus under all climatic conditions. j

Moreover, such prior art devices have been subject to deterioration due to moisture or other conditions accompanying climatic changes, whereby the efficiency and operation of the device have been impaired.

In View of the above-mentioned disadvantages prevailing in the prior art devices, one of the objects of the present invention is to provide a novel heated Pitot-static tube whereby such disadvantages are eliminated.

Another object is to provide a novel electrically heated Pitot-static tube device whereby sleet, snow, ice formation or other impediments, to the free operation of the device are prevented.

Still another object is to provide a novel electrically heated Pitot-static tube comprising an electric heating element completely sealed against moisture. 1

A further object is to provide a novel electrically heated Pitot-static tube, comprising a heating wire covered with electrical insulation and completely sealed in a Waterproof shell, said wire and shell being wound into a heatingcoil with the adjacent turns thereof. soldered or brazed together to form a unitary heatlng'element.

Still another object of the present invention is to provide a novel electrically heated Pitotstatic tube, comprising a heating wire, a heat conducting sheath providing a moisture proof covering for said wire and electrical insulating means between said Wire and sheath, said wire and sheath being formed into a coil with a, section of the wire and sheath extending away fromV said coll, whereby heat distributingv means are provided remote from said coil proper.

The above and further objects and advantages v0f the invention will appear morefully herein- 55 after from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein a, plurality of embodiments of the invention are illustrated. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only and is not designed as 'a denition of the limits of the invention, reference being primarily had for this purpose to the appended claims.

In the drawing, wherein like reference characters refer to like parts throughout the several views;

Fig. 1 is an elevation, partly in section, illustrating one form of the novel Pitot-static tube embodying the present invention;

Fig. 2 is a section taken on a line 2--2 of 1; and K Fig. 3` is a view, in cross-section, illustrating another embodiment of the invention.

Referring to the drawing, and more particularly to Fig. l, the invention is shown in the present instance as applied to'a Pitot-static tubelll Fig.

comprising a metal tubular section I I having a threaded portion I2 attached to a threaded portion I 3 of the tube casing I4, the latter casing being provided with a suitably tapered end.

'I'he tubingl Il is provided with an opening I5 and constitutes the velocity-pressure end of the Pitot-static tube forl transmitting pressures due to velocity-head to an airspeed indicator, for example. Casing I4 is provided with a plurality of apertures I6 in the walls thereof utilized for transmitting pressures due to static or pressurehead. Coinciding with the opening I5 at the end of tube II and extending within the latter is a tube Il mounted in a bore I8. formed in the threaded portion I3.

Mounted within tube Il is another tube I9 provided with a baiie 20 and a notched-out opening 2|. The notched-out opening 2| and baille 20 combine to provide means for conveying the velocity-head to the device to be actuated, baiiie 2li preventing entrance of any foreign matter into the tube I 9. Similar means in the form of a tube or chamber Ma are provided whereby the-static or pressure head is likewise^conveyed to the device to be actuated.

When an aircraft on which the Pitot-static tube is mounted is flying at high altitudes in which very low temperatures are prevalent, or when ying during inclement weather, ice tends to form or snow tends to pack at the openings I5 or 2l or within the interior of the velocity-tubing I9, thereby clogging the same or completely closi comprise a copper, steel, or other electrical current (not shown) whereby the coil y may be heated.

In the present embodiment, coil 22 comprises an electrical .heating wire 23 surrounded by or protected from a metal casing or sheath 24 by heat resisting insulation 25 which may be, for example, felted asbestos placed around the wire 23, or a series of minute porcelain beads separating the wire 23 from casing '24. `Casing 24 may highly heatconducting metal which may, if desired, be drawn over the wire 23 and insulation 25 or wire 23 and insulation 25 may be inserted therein, thereby producing a compact structure insuring greater heat propagation. The complete assembly of wire 23, insulation 25, and sheath 24 is then formed into a coil by winding the complete wire assembly about a section 23a for example, of said assembly wire as a base, as shown in Fig.l 2, or the assembly may be formed into any desired geometrical shape.

Coil 22 is surrounded by a metal sleeve 26 located between coil 22 and the metal tubeil and in contact therewith. A perforated disc of insulation 21 mounted on tube i1 closes the end of the metal sleeve 264 and is held in abutting relation therewith by resilient ring 28 abutting a wall I la of the tube il. The sleeve 26, in the present instance, is of highly heat-conductive metal such as beryllium copper, for example, sol that heat from coil 22 is conducted readily to tube Il.

The extremities zza, zzb of een zz extend into conduits formed by metallic tubes 29 and 30 respectively, mounted in the casing I4. Said extremities extend through the static chamber I4a formed within thecasing I4 and thereby provide means ior distributing a portion of the heating effect of coil 22 into the chamber Ha and about the velocity-tubing leading to the device to be operated, so thatany moisture from the melted ice or snow is prevented from forming any obstruction within the velocity-tubing. The ends 23a and 23h of heating wire 23 are connected to suitable binding posts (not shown) which in turn may be both connected to the terminals of a suitable source of electrical energy or one end may be grounded to the Pitot-static tubeacasing when it is .desired to utilize a single-wire-groundreturn-system.

In Fig. 3 there is illustrated another embodiment of the present invention, in which the composite wire comprising heating wire 23, insulation 25, and casing 24 is wound into a double layer coil 22e, thereby providing a highly eilicient heating element capablev of preventing obstruction of the Pitot-static tube under any climatic conditions. v

In the embodiment as illustrated in Figs. 1 and 2, the adjacent layers may be soldered or brazed together, whereby a unitary) heating element is produced of very high efficiency, while in the embodiment illustrated in 3. the superimposed layers and-the adjacent layers may also be the heating effect of wire 23 soldered'or brazed together to provide a highly enlcient unitary heating element.

IIn the operationof the device, the heating unit comprising several turns of the composite wire, provides a large radiating surface due to the larger circumference of the sheet 24, whereby is eiiiciently distributed to the velocity-pressure conducting tubing and the wire 23 is furtherV completely encased in a waterproof sheath whereby deterioration or short-circuiting of the heating element due to penetration `of moisture is completely obviated. y

There is thus provided a novel heated Pitotstatic tube structure, whereby the heating eiiect l of the heating element is efiiciently conducted to the velocity-pressure tubing, and distributed throughout the length thereof and whereby deterioration of the heating element is prevented. Although only two embodiments of the invention have been illustrated and described, various changes and lmodifications in form, materials, and relative arrangement of parts, which will nowappear to those skilledin the art, may be made without departing from the scope of the lnvention.` Reference is therefore to be had to the appended claims for a denition of the limits of the invention.

What, is claimed is:

1. A Pitot-static tube comprising a tubular metallic hollow body having its rear end tapered and closed and its front end open for receiving the impact of dynamic pressure, a wall dividing said tubular body into front and rear compartments, said rear compartment .havingV static openings in its wall and constituting a static pressure chamber, a dynamic pressure tube extending through said rear compartment into said front compartment through said dividing'walll with the open end of said pressure tube positioned at the open front end of said tubular body to receive thefimpact of dynamic air pressure, an electrical heating coil located in the front compartment of said tubular body and surrounding heated by the heat of the heated air passingr through said pressure tube.

2. A Pitot-static tube comprising a tubular metallic hollowbody havingits rear endtapered and closed and its front endhopen for receiving the impact of dynamic air pressure, a wall dividing said tubular body into front and rear compartments, said rear compartment having staticopenings 'in its wall and constituting a static pressure chamber, a dynamic pressure tube extending through said rear compartment into said front compartment through said dividing wall with the open end of said pressure tube positioned at the open front end of said tubular body -to receive the impact of dynamic air pressure, an electrical heating coil located in the' front compartment of said-'tubular body and surrounding said pressure tube in heat conducting relation therewith to heat the -air passing therethrough,

and at least one heat conducting metal tube sealed in an opening in said dividing wall and Iprojecting from said wall rearwardly along said static chamber, said coil being made of wire having a heat conducting metal sheath covering the same but electrically insulated therefrom, and 

